Enhancing surface stabilization of CH3NH3PbI3 perovskite by Cl and Br doping: First-principles study

In this study, the effects of Cl and Br surface doping on the surfaces' structural stability of CH3NH3PbI3 (MAPbI3) perovskite have been investigated using the density functional theory. Its aim is to pursue how to stabilize a flat surfaces structure (no vacancy) of the MAPbI3 perovskite in overcoming its chemical instability. In this calculation, the (001) texture of the MAPbI3 perovskite surface was modeled as a prototype. The 216-atom and 264-atom supercells were employed to imitate the Lead Iodide (PbI2)- and Methylammonium Iodine (MAI)-terminated surfaces, respectively. It was found that doping of either Cl or Br atoms on perovskite surfaces enhances the energies required for releasing PbI2 and MAI molecules from the surfaces, causing vacancies on the surfaces. This is owed to the binding energies between the Cl and Br dopants and their surrounding atoms on the surfaces being stronger than those created by the Iodine atom. This implies that the formation of surface vacancies—which causes perovskite's degradation—can be prevented by Cl and Br surface doping. The obtained results elucidate the capability of Cl and Br dopants on surface stabilization, describing why one should incorporate Cl/Br into MAPbI3 to overcome instability issues and enhance the efficiency of the MAPbI3-based perovskite solar cell.